What are the latest preventive measures for onion bolting?
When growing onions, bolting often occurs. Onion bolting, also called premature bolting, refers to the bolting phenomenon that occurs before the onion bulb has grown to a certain size. It can seriously affect onion yield and cause huge losses for farmers. The main cause of onion bolting is mainly low temperature. How should it be prevented? Let's take a look together.
1. Sow at the right time and reasonably
Choosing a suitable sowing time is not only a key point for preventing onion bolting, but also a key point for high yield. Generally, late September to mid-October is the right time for sowing. Sowing at this time can avoid the drawbacks of excessive seedling growth and a high bolting rate caused by sowing too early, and can also avoid the phenomenon of low yield caused by too little seedling growth from sowing too late. In addition, the density should be controlled when sowing. If sowing is too sparse, the seedlings grow too large and the bolting rate will also rise; if sowing is too dense, it will also cause lower yield and make the plants more susceptible to pests and diseases.
2. Suitable transplanting
As with sowing, the time of transplanting is also extremely critical. Generally, transplanting is best done from November to December. During this period, choose strong seedlings for transplanting. After the Spring Festival, the seedlings begin to grow, the bolting rate is low, and yield can be increased. If the transplanting time is improper, the seedlings will grow too much during overwintering and then enter a peak growth period after the Spring Festival, resulting in a high bolting rate and low yield.
3. Fertilizer and water management
Onions should not be topdressed during overwintering. After the Spring Festival, heavy fertilization should begin 3 times: the first time in mid-March, the second time in mid-April, and the third time in early May. Each time, 15-25 kg of urea and 5-7 kg of potassium sulfate can be applied per mu, or decomposed organic fertilizer or compound fertilizer can be applied. This promotes vegetative growth of the seedlings, thereby inhibiting reproductive growth and reducing the bolting rate.
4. Strengthen field management
If onion plants are found to have bolted, the flower heads can be removed manually to prevent excessive consumption of nutrients, but do not remove the hollow leaves, so as to prevent rain or pathogens from invading and causing rot. In addition, hormone agents can be sprayed, which have a certain inhibitory effect on bolting. 0.25% ethephon or 0.16% maleic hydrazide can be sprayed at the seedling stage or after flower bud differentiation, with an obvious inhibitory effect.
The above are preventive measures for onion bolting. We hope they can help you. To learn more related knowledge, please keep following us.